1. Field of the Invention
The present invention relates to structural joints, and, more particularly, to improved joint structures for enclosures, particularly those fabricated from sheet metal.
2. Description of the Prior Art
Enclosures for equipment and mechanisms are quite common. An enclosure may serve one or more protective functions, including preventing personnel from coming into contact with potentially hazardous items within the enclosure and preventing noxious substances within the enclosure from escaping into the surrounding environment.
Aside from such protective functions, equipment enclosures at times also perform functions in aid of, or necessary to, the function of the contained equipment. For example, in the case of HVAC equipment which includes fans or blowers, an enclosure both prevents personnel from contacting rotating members and defines and encloses a volume. The enclosure permits the fan or blower to maintain the enclosed volume at a negative or positive pressure. Ducts or the like connected to the enclosure are thus able to conduct air to or from the enclosure due to the action of the fan or blower.
In some HVAC equipment configurations an enclosure may surround a burner, various damper structures and a blower. Often the output of the blower is run through a wall of the enclosure and directly connected to ducts which carry air at a positive pressure which has been heated by the burner. The return ducts carrying air to the burner to be heated thereby are connected directly to the enclosure for communication with the interior thereof. The interior of the housing is in direct communication with the input side of the blower, and is, accordingly, maintained at a negative pressure.
If the enclosure is not integral, or if joints between various structural members thereof, as well as connections to ducts, are not well sealed, the negative pressure maintained within the interior of the enclosure will tend to draw into the enclosure undesirable substances. In indoor environments, such substances include water vapor; in outdoor environments, such substances include liquid water from rain and other precipitation. The corrosive and other deleterious effects of water are well known as are the benefits of excluding water from the interior of the enclosure. Other corrosive or deleterious substances, such as gases or solvents, may also be drawn into the enclosure by a negative pressure therewithin.
Enclosures surrounding the fans, blowers or other elements of HVAC equipment must also be robust. They must be able to withstand the positive or negative pressures maintained therewithin and to provide firm, rigid mounting environments for the fans and blowers, as well as for burners, ductwork and other items associated with the HVAC equipment.
Typically, enclosures of the type discussed above are fabricated from pieces of sheet metal which are connected together at and by joint structures. Ideally, these joint structures should permit the sheet metal to be attached thereto in a manner which, with a minimum of effort and expense, minimizes or eliminates infiltration of water and other substances into the enclosure. Further, the joint structures should also permit the expedient construction of a robust enclosure.